The present invention relates generally to the field of switch mode power supply (SMPS). More particularly, the present invention relates to power supply control circuits that have a fast startup time.
In 1955, an American G. H. Roger invented the self-oscillation push-pull transistor single transformer DC-DC converter, which was the beginning of high-frequency switching conversion control circuit. In 1957, Jensen invented the self-oscillating push-pull dual transformers. In 1964 U.S. scientists proposed the abolition of frequency transformer series switching power supply, which pointed to a fundamental way of decreasing the size and weight of power supplies. By 1969 because of improved components, such as higher voltage tolerance of high-power silicon transistors and shortened reverse recovery time of diodes, 25 kHz switching power supplies were realized.
Currently, switching power supply products have been widely used, because of their small size, light weight, and high power conversion efficiency. For example, they are used in industrial automation and control, military equipment, scientific equipment, LED lighting, industrial equipment, communications equipment, electrical equipment, instrumentation, medical equipment, semiconductor cooling and heating, air purifiers, electronic refrigerator, LCD display, audio-visual products, security, computer chassis, digital products, equipment, and other fields.
For switching power supplies, the start time is one of the important parameters. Along with the extensive application of switching power supply, fast startup time is becoming more and more desirable to the users. As explained below, conventional methods of achieving faster startup time has many drawbacks.